Method of making leather water-repellent



United States Patent 3,010,780 METHOD OF MAKING LEATHER WATER-REPELLENT Jiirgen Plapper and Rudi Heyden, Dusseldorf, Germany, assignors to Bohme Fettchemie G.m.b.H., Dusseldorf, Germany, a corporation of Germany v No Drawing. Filed Mar. 25, 1958, Ser. No. 723,659 Claims priority, application Germany Mar. 30, 1957 11 Claims. (Cl. 8-84.26)

This application is a continuation-in-part of copending application Serial No. 550,212, filed November 30, 1955, now abandoned.

This invention relates to a method of making'leather water-repellent.

Broadly stated, we have found that leather is rendered water-repellent by depositing within the tanned animal hide a complex compound formed by a mineral-tanning agent with a tribasic or higher polybasic 'acid derivative containing a hydrophobic group. The .term hydrophobic group as used herein is well known in the chemical arts and has been defined by Schwarti and Perry in their publication Surface ActiveAgents," Interscience Publishers, Inc., New York (1949), on pages 17-19 as follows:

In view of these considerations it is important to examine some of the more usual types of hydrophobic groups and the ways in which they are obtained.

(1) The straight alkyl chains of eight to eighteen or more carbon atoms are derivedfrom the natural fatty acids. These may be used as such or may be converted to acid chlorides for use in acylation reactions. The acids or their esters may also be reduced to the corresponding fatty alcohols or through the nitriles to the fatty amines. These in turncan be used as intermediates in a variety of reactions to introduce the long alkyl chain. The natural fatty acids are possibly the most important raw material for hydrophobic groups. A wider variety of detergents has been derived from them directly or indirectly, than from any other single source.

(2) The lower alkyl groups of three to eight carbon atoms are frequently attached to aromatic nuclei such as benzene or naphthalene, the combination forming a useful type of hydrophobic group. The sources of lower alkyl groups are usually the alcohols. The lower alkyl groups are sometimes used by themselves as hydrophobic groups, as in the case of the dialkyl sulfosuccinates:

(5) Certain types of petroleum yield naphthenic acids in the normal course of refining. These are surface active in themselves and have also been used as a source.

of hydrophobic groups in derived surface active agents. In the refining of petroleum oils by washing with sulfuric acid the surface active petroleum sulfonates are obtained.

More particularly, we have found that water-repellent leather is obtained by either of two methods:

In either case, the mineral-tanning agent furnishes the ion for the formation of the complex compound in situ "ice in the tanned hide. Examples of particular mineraltanning agents are chrome, aluminumand iron-tanning agents. Among aluminum-tanning agents, basic aluminum salts, and especially aluminum sulfate and alum, are particularly suitable.

In general, organic compounds which we have found to be suitable for this purpose are derivatives of tribasic or higher polybasic inorganic or organic acids which contain hydrophobic radicals and at least two free, saltforming groups capable of combining with the mineraltanning agent to form an organometallic complex grouping. Such'polybasic acid derivatives have acid characteristics and are preferably used for the purpose set forth in the form of their water-soluble salts, especially those formed by neutralization with organic bases, their ammonium salts and alkali metal salts.

Examples of suitable inorganic polybasic acids upon which the above derivatives are based are boric acid, phosphoric acid, arsenic acid and the like. Similarly suitable organic polybasic acids are, among others, citric acid, trimesitinic acid, trimellitic acid, mellitic acid, diadipic acid, ethane-tetraacetic acid, sulfophthalic acids, oxyphthalic acids, pyrogallic acid, pyrogallol carboxylic acids, and, the like. Other suitable organic acids are those which contain hydrophobic radicals and may, for example, be obtained by subjecting high molecular weight unsaturated fatty acids, fatty alcohols or olefins to a condensation reaction with maleic acid, such as the condensation products of oleic acid, linseed oil fatty acid, soybean oil fatty acid, and the like, with one or several mols of maleic acid.

While the above high molecular weight tribasic or higher polybasic carboxylic acids may be used without modification to form organometallic complex compounds with the mineral-tanning agent, the tribasic or higher polybasic inorganic acids or the low molecular weight tribasic or higher polybasic carboxylic acids disclosed above are preferably transformed into compounds having an afiinity to form complexes with the mineral-tanning agent, by partial esterification or partial amidation with high molecular alcohols or amines, respectively. The resulting products are either well-known materials or are readily obtainable by methods known in the art. In place of these particular compounds, any other suitable compounds may be used, provided they contain at least one hydrophobic radical and at least two salt-forming radicals capable of forming complexes with the mineraltanning agent.

Examples of some specific compounds which are capable of forming complexes with the mineral-tanning agent and which may be used to increase the water-impermeability of leather in accordance with the present invention are the following: acid dodecylphosphate, acid octadecenylphosphate, hexadecylborate, octadecenylarsenate, hexadecylcitrate, acid dodecylsulfophthalate, citric acid mononaphthenyl amide, citric acid monooctadecyl amide, and the like. Such compounds may be employedas such or in the form of their water-soluble salts.

The hydrophobic radicals of these compounds may be of an aliphatic, cycloaliphat-ic, aliphatic-aromatic or aliphatic-cycloaliphatic nature, and maybe interrupted by oxygen, nitrogen or sulfur atoms or carry substituent radicals comprising oxygen, sulfur or nitrogen atoms. Of particular interest are, for example, tribasic or higher polybasic organic or inorganic acids esterified with high molecular weight ethoxylated fatty alcohols, especially high molecular weight fatty alcohols ethoxylated with 1 to 10 mols, preferably 1 to 3 mols, of ethyleneoxide per mol of alcohol. The waterproofing treatment of leather with aqueous solutions or dispersions of these compounds, is carried out in accordance with the usual procedures; for ex-' these examples. 1 1

. dispersion, or by brushing the solution or d-ispersion onto the leather. The amount of such compounds which is generally required to achieve the desired waterproofing eifect ranges from 0.5 to based upon the shaved weight of the leather, but amounts from 1.5 to 5% are preferred.

The polybasic acid. derivatives used in accordance with this invention inherently possess fatting properties. Consequently, depending" upon the quantity of such derivatives used, the leather need not be fat-liquored at all or the amount of fat-liquoring agent applied to the leather can be substantially curtailed.

A further improvement ofthe water-repellent properties of leather can be achieved by employing the poly- 7 basic acid derivatives herein disclosed, slightly in excess, and thereafter treating the leather with small quantities of a commercial mineral-tanning agent,- fat liquoring and finishing in the customary manner. This subsequent treatment of" the waterproofed leather with small amountsofmineral-tanning agent renders still soluble components which may have been absorbed by the leather insoluble. In other words, this treatmentas-.

sures that all of the polybasic acid derivative availabletoform metal complexes has been transformed into such waterrepellent complexes.

Another method of improfi'ng the water-repellent char acteristics of the leather impregnated in accordance with the present invention is heatingthe finished and dried leather 'to' temperatures. up toabout 90 C. forextendedperiods of 'tinie. a As previously mentioned, the waterproofing treatment describedherein may also be applied in conjunction with a combination vegetable-and-mineral-tanning procedure.

.For example, a vegetable-tanned leathermay be 'first treated with the: hydrophobic polybasic compounds: and

subsequently treated withmineral-tanning agents. Hence, it is possible to achieve-vegetable or combination tan-' ning. effects along with the Water-repellent effect, depending upon' the amount of vegetableand mineral-. tanning agents employed.

The waterproofing treatment according to the present invention may be applied to all types o lf'mineral-tanned and combination-tanned leather, and is particularly advantageous' when used in conjunction with suede leather whose water-repellent characteristics are often unsatis factory. The waterproofing treatment increases the water-permeability quotient of untannedski-ns inmost. cases by 100%, for example to about 1.8, While the normal water-absorption capacity is reduced by about" one-halfi without, however, impairing the air-permeabil ity of the leather. Another particular advantage oftheprocess accordingto the present invention is that it permits the manufacture of light-colored; particularly white:

- aluminum-tanned leather having extraordinary waterrpel-lent properties;

The following-exampleswil-l further illustrate the present' invention' and enable others skilled in the art to understand it more completely. We wish it to be understood, however, that we do not intend to limit ourselves to the particular compounds" and conditions recited in Example I Chrome-tanned and neutralized. cow hides were im: mersed for- 45 to 60 minutes at a temperature of, 50.? C. ina solution consisting of 100 to 150% water. and 1 to 5% ofithe ammoniumsalt of an acid. phosphoric acid. dodecyl estenbased upon the shavedweight of the hides being. treated. Subsequently, the impregnated leather wasdyed in the customary manner and fat-liquoredwith a commercial fat-liquoring agent to. achieve the desired .suppleness.

The leather was then finished.v in the customary .manner. The resulting leather was not. only of high quality but also. showed improved. water-repellent characteristics.

Example II Chrome tannedQdyed and neutralized cow hides were immersed in the waterproofing solution as described in Example I. Thereafter, the impregnated leather was chrome-tanned in a separate vessel with a commercial chrome-tanning agent containing 0.5 to. 1% Cr O fatliquored and finally dried in the customary manner. The Water-repellent: properties: of the. resulting. finished leather were; even-more improved than those of the leather obtained in. Example; I. a

Similar results were obtained when the dry finished leather of Example I, was heated to about 90 C'. for 45 minutes to 1 /2 hours.

Example III Bark-tanned cow hides were immersed for 45.. to 60 minutes in a solution consisting of 100 to, 150% water at 50 (-3. and 1 to 5% of the ammonium salt of the. monooleyl. ester of citric acid, based upon. the shaved weight of the hides being treated. Thereafterpt'he. impregnated leather was chrome tanned with 0.5 to 1% C50 inthe form of a commercial 3 3 basic chrometanning agent, fat-liquorecl and then finished in the custernary manner. Theresultit gleather is oi high quality and has eX'cellentwater-repellent characteristics.

Example IV Chrome-tanned and neutralized calf skins were 1111-- mersed for 45 to 60 minutes, in an aqueous. solution consisting oti 100;to. 15.0,%I w'atcr andflf to. 5%.. of the am: monium. salt, of the condensation product obtained by condensing 1 mol linseed oil fiat ty acid and 1 to 2 mols maleic acid. ,T'liereafter, the, impregnated latherwas finished as desctigliedin Example, I. Ihe'.resu-lting-leather was alsoofi quality andlia'd. excellent waterrr'epehen-t proper ies. i V i Example V f 1 to ofithe ammonium. salt of the acid. diadipic acid didodecylesten.was'used'instead of the ammonium salt of an acid: phosphorio acidi dodecylester in Example- I. A high qualityi leather haning goods water-repellent:

acid octadecylester was used instead of the ammonium mononaphthenylestcr, was substituted for the, ammoniumsalt of an acid phosphoric acid dod'ecylester in Example I. A high quality leather having goodwater-repellent properties wasobtained. 1

. v 7 Example VIII I i l to 5%. of-the ammoniumsalt ofthe acid arsenic acid salt of themonooleylester of citric acid, in. Example III. An. excellent, water-repellent leather, was. obtained.

ExampleJX ay, w

Example XI 1 to 5% of the ammonium salt of the condensation product from 1 mol soyabean oil fatty acid and 1 to 2 mols maleic acid was used instead of the ammonium salt of the condensation product from 1 mol linseed oil fatty acid and 1 to 2 mols maleic acid of Example IV. A leather was obtained which had good water-repellent properties.

Example X11 1 to 5% of the ammonium salt of the trimellitic acid monooctadecylamide was used instead of the ammonium salt of the condensation product from 1 mol linseed oil fatty acid and 1,to 2 mols maleic acid of Example IV. A leather was obtained which had good water-repellent properties.

Example XIII Aluminum-tanned and neutralized sheep hides were soaked for 45 to 60 minutes in a drum containing 100 to 150% water at 50 C. and from 1 to 5% of the ammonium salt of an acid phosphoric acid monododecylester, both percentages being based upon the shaved weight of the hides. Subsequently, the impregnated hides were removed from the drum and dyed in the customary fashion, and then fat-liquored with a commercial fatliquoring oil to achieve the desired suppleness. The leather may, however, also, be dyed prior to the im pregnation with the phosphoric acid ester salt. The.

Example XIV Delimed and bated sheep skins which had been degreased to the desired degree were soaked in 100% water at 20 C. in a rotating drum. 'From 0.5 to 1.5% formaldehyde were added in small portions to the soaking water and after 15 to 30 minutes the pH of the'soaking solution was slowly adjusted to between 8 and 8.5. Total running time: 1 to 2 hours. The tanned pelts were then stored overnight on the horse and the following morning they were retanned with 1% A1 in the form of a basic commercial aluminum tanning agent or with potassium aluminum alum (100% solution; running time: about 1 /2 hours). Prior to the retanning step, the pelts may also be soaked for some time in an acid solution or in a weak formic acid pickling bath. After rinsing the aluminum-tanned pelts and neutralizing them, they were impregnated with 1 to of the ammonium salt of an acid phosphoric acid monododecylester. The impregnation effect was further improved by retanning the skins in a separate bath with 0.5 to 1% Al O in the form of a commercial aluminum tanning agent or potassium aluminum alum. All of the above percentages are based upon the shaved weight of the skins. After fatliquoring to the desired degree and drying the skins in the customary fashion, a white, soft, supple, light-stable leather was obtained which also exhibited excellent water-repellent properties.

Example XV Leather completely tanned with light natural tanning agents or synthetic white tanning agents was either dyed with light pastel dyes or was allowed to remain white. Thereafter it was soaked in a solution containing from 1 to 5% of the ammonium salt of a high-molecular-weight polycarboxylic acid which had been obtained by the reaction of 1 mol linseed oil fatty acid with l to 2 mols maleic acid. The impregnated leather was then treated as described in Example XIII .aud retanned with from 0.5 to 1% A1203. The retanned leather was then fat-liquored with a commercial fat-liquoring oil to the desired degree of suppleness. A white or pastel-colored, supple, lightfast leather was obtained, which also exhibited excellent water-repellent properties. The above percentages are also based upon the shaved weight of the skins.

Example XVI White leather tanned with melamine resin or dicyandiamide resin was rinsed and then soaked in a solution containing 100 to 150% water at 50 C. and 1 to 5% of.

the ammonium salt of an acid phosphoric acid monododecylester (running time: 40 to 60 minutes). Thereafter the skins were retanned in a separate bath containing to 100% water and 0.5 to 1% A1 0 in the form of a commercial aluminum tanning agent or potassium aluminum alum (running time: about 2 hours). The retanned leather was then fat-liquored as needed to the desired degree of suppleness and dried in the customary fashion. The water-repellent effect was increased by subjecting the dried leather to temperatures of about C. for a short period of time. A white, water-repellent apparel leather was obtained.

While we have illustrated our invention with various specific embodiments, it will be obvious to persons skilled in the art that various changes andmodifications may be made without departing from the spirit of the invention pound selected from the group consisting of (a) esters and amides of tr-icarboxylic and higher polycarboxylic organic acids and tribasic and higher polybasic inorganic acids, said esters and amides containing at least one organic hydrophobic waterproofing radical in the ester and am-ide moiety and (b) condensation products of high molecular weight unsaturated fatty acid with maleic acid, said compound containing at least two free, saltforming groups capable of forming an organornetallic complex with metallic ions in the mineral-tanning agent, and (2) a mineral-tanning agent selected from the group consisting of chrome-, aluminumand iron-tanning agents, and drying the impregnated hides.

2. The method of making mineral-tanned animal hides water-repellent, said hides being tanned with a mineraltanning agent selected from the group consisting of chrome-, aluminum-, and iron-tanning agents, which comprises impregnating said hides with an anionic 'watermiscible compound selected from the group consisting of (a) esters and amides of tricarboxylic and higher polycarboxylic organic acids and tribasic and higher polybasic inorganic acids, said esters and amides containing at least one organic hydrophobic waterproofing radical in the ester and amide moiety and (b) condensation products of high molecular weight unsaturated fatty acid with maleic acid, said compound containing at least two free, salt-forming groups capable of forming an organometallic complex compound with said mineral-tanning agent, and drying the impregnated hides.

soluble salt of an at least tricarboxylic organic polycarhoxylicaeid ester, said acid: ester containing organic hy drophobic waterproofing radicals and said acid ester con taining at least two free, salt forming groups capable of forming organometallic complex compounds with said mineral-tanning agent, and drying the'impregnated hides. 5.. The method of: making minerahtanned animal hides ywat'er-repellent, said hides being tanned with av mineraltanningagent selected from the group 'consisting of chrome, aluminum-, and iron-tanning agents, which comprises. impregnating. said hides with an anionic watersol-ubie'fsalt of an at least tricarboxylic organic poly carboxylic; acid amide, said acid amide salt being derived from an amine containing hydrophobic alkyl radi cals and said acid amide salt containing at least two free, salt-forming groups capable of forming onganometallic complexz' compounds with said mineral-tanning agent, and drying the impregnated hides.

6'. 'Fhemethod of making mineral-tanned animal hides water-repellent, said hides being tanned with a mineraltanning" agent. selected from r the" group consisting. of

chrome, aluminum-, and iron-tanning 'agents,' which comprises impregnating-said hides with an anionic Water miscible compound selected from the group consisting of (a) esters and amides of at least tricarboxylic organic acids and at least tribasic inorganic acids, said esters and amides containing at least one organic hydrophobic; waterproofing radical inthe ester and amide moiety and ('b condensation products of molecular weight unsaturatedfatty acid with maleicacid, sm'd compoundcontaining at least two free, salt-forming groups capable; of forming. an: organometallic complex compound with said, mineral-.tanningagent, the amount of said water-miscible compound being in excess of that re-- quired to combine with all ofsaidmineral-tanning agentin the hides to. form: said organometallic complex, re-

tanning the impregnated hides with amineral-tanning agent selected from the groupconsisting of chrome-,.

aluminum-, and iron-tanning agents, and drying the retannedhides;

.TJ'The method: of making tanned animal hides waterrepellent, which comprises impregnating said hides with a complex organometallic compound formed by interaction in. situ of (1). an anionic water-miscible compound selected from the group consisting of (a) esters and amides of tricarb'oxylic and higher polycarboxylic organic acidsyand tribasic and higher pol'ybasic inorganic acidsg-said esters and amides containing at least one organic hydrophobic waterproofing radical in the esterand amidemoiety, and- (b) condensation products of a high molecular: Weight unsaturated fatty acid with. maleic acid, said: compound-containing at least two'free, salt-forming. groups capable of forming 'anorgano-metallie. complex withmetallic ions in the mineral-tanning agent, and. (.2) a mineral-tanuing .-agent selected from the group consisting of chrome-, 'aluminumand irontanning. agents, drying the impregnated hidesandheating thedried hidesto about 90'? C.

8. The method of'making mineral-tannedanimal hides. Water-repellent, said hides being tanned with a mineral- V tanning agent selected from the group consisting of chrome, aluminium, and irori-tanning agents, which comprises impregnating said hides with an anionic watermiscible compound selected from the group consisting of (a) esters and amides of at least tn'oarboxylic organic acids and at least tribasic inorganic acids, said esters and amides containing at leastone organic hydrophobic water-proofing radical in the ester and amidemoiety, and (b) condensation products of a high molecular' weight unsaturated fatty acid with maleic acid, said compound containing at least two free, salt-forming groups capable of forming .an onganom-etallic complex compound With said mineral-tanning agent, the amount of said water-miscible compound being in excess of that required to combine with all of said mineral-tanning agent in the hides to form said organometalliccomplex, retanning the impregnated hides with a mineral-tanning agent selected. from the group consisting of chrome, alu- .n1inum;, and iron-tanning agentsidrying the retanned hides and heating the dried retanned hides to about 90 C.

9.. The. method of making non-mineral-tanned leather water-repellent, which comprises impregnating said. leather with. an anionic water-miscible.compound select.- ed from the. group consisting of (a) esters and amides Of at least tricarboxylic organic acids and at least. tribasic inorganic acids, said esters and amides containing at least one organic. hydrophobic waterproofing radical in; the. ester and amide; moiety, and (b) condensation products. of a high. molecular weight. unsaturated fatty acid with maleic acid, said compound containing at. least two, free, salt-forming groups capablev of forming an: organometallic: complex. compound. with a mineral-tanning agent, retanning the impregnated hides with a mineraltanm'ng agent selected. from the group consisting of chrome-, aluminum.-, and iron-tanning agents, anddrying the retanned, hides.

. 10. Themethod; ofmaking tanned animal hides waterrepellent, which comprises impregnating said hides with a complex organometallic compound formed by inter action in situ of an anionic water-miscible salt of a tribasic acid ester, said acid; ester containing: at least one alkyl chain having. 8 to. 1.8. carbonatoms; and at least two free, salt-forming groups capable oi; forming; an organemetallic complex with metallic ions in the. mineralrtanning. agent, anda; chrome mineral-tanning agent, and. dry-' ing the impregnatedv hides.

' 1.1. The methodof making tanned animal hides. water.- repellent, which comprises impregnating said hide with actioninv situ of an anionic water miscible salt. of a tribasic acid ester, said acid ester containing at least one alkyl; chain having 8 to 18. carbonatoms. and at least two free; salt-forming groups capable of forming an organo-- metalliccomplex with metallic ions: in the mineral-tanning agent, and an aluminum mineral-tanning agent, and

drying the impregnated hides.

References Cited in the file'of'this patent UNITED STATES- PATENTS 2,115,509 Jaeger .Apr. 26, i938. 2,693,996 V011 Fuchs NOV. 9,1954 2,772,988 Plapper et a1, .De.c. 4, 1956 2,322,235

Heyden et a1 Feb. 4, 195,8 

1. THE METHOD OF MAKING TANNED ANIMAL HIDES WATERREPELLENT, WHICH COMPRISES IMPREGNATING SAID HIDES WITH A COMPLEX ORGANOMETALLIC COMPOUND FORMED BY INTERACTION IN SITU OF (1) AN A ANIONIC WATER-MISCIBLE COMPOUND SELECTED FROM THE GROUP CONSISTING OF (A) ESTERS AND AMIDES OF TRICARBOXYLIC AND HIGHER POLYCARBOXYLIC ORGANIC ACIDS AND TRIBASIC AND HIGHER POLYBASIC INORGANIC ACIDS, SAID ESTERS AND AMIDES CONTAINING AT LEAST ONE ORGANIC HYDROPHOBIC WATERPROOFING RADICAL IN THE ESTER AND AMIDE MOIETY AND (B) CONDENSATION PRODUCTS OF HIGH MOLECULAR WEIGHT UNSATURATED FATTY ACID WITH MALEIC ACID, SAID COMPOUND CONTAINING AT LEAST TWO FREE, SALTFORMING GROUPS CAPABLE OF FORMING AN ORGANOMETALLIC COMPLEX WITH METALLIC IONS IN THE MINERAL-TANNING AGENT, AND (2) A MINERAL-TANNING AGENT SELECTED FROM THE GROUP CONSISTING OF CHROME-, ALUMINUM-AND IRON-TANNING AGENT, AND DRYING THE IMPREGNATED HIDES. 